Gastroesophageal reflux disease (GERD) is a common condition where stomach acid flows back into the esophagus, causing heartburn. Coffee is a frustrating trigger for these symptoms, often forcing people to choose between their morning ritual and digestive comfort. The compounds in a typical cup of coffee interact with the digestive system in ways that exacerbate reflux. This conflict has led sensitive drinkers to explore alternative preparation methods, such as cold brewing, to find a gentler way to enjoy their beverage.
Coffee Compounds That Trigger Reflux
The irritating effects of coffee stem from a complex interaction of chemical compounds. A primary culprit is caffeine, which stimulates the production of gastric acid in the stomach. Caffeine also causes the lower esophageal sphincter (LES)—the muscular valve separating the esophagus and stomach—to relax. When the LES relaxes improperly, stomach contents and acid can more easily flow backward into the esophagus, initiating a reflux episode.
Beyond caffeine, two major groups of compounds contribute to coffee’s digestive impact: chlorogenic acids (CGAs) and N-alkanoyl-5-hydroxytryptamides. Chlorogenic acids are naturally occurring antioxidants in the coffee bean that contribute to coffee’s overall acidity and flavor. When heated during the roasting process, some CGAs can degrade into other acids, such as quinic acid, which may further irritate the stomach lining.
N-alkanoyl-5-hydroxytryptamides are waxy compounds found on the surface of the coffee bean that have been specifically linked to stimulating the stomach to produce more acid. These compounds, along with CGAs, can increase the stomach’s acid output, creating a larger volume of irritating fluid available to reflux.
The Chemistry of Cold Brewing
Cold brewing fundamentally alters the chemical composition of the final beverage by using time instead of high heat for extraction. The process involves steeping coarsely ground coffee in cold or room-temperature water for an extended period, typically 12 to 24 hours. The primary mechanism at play is the principle of temperature-dependent solubility.
Hot water is a highly efficient solvent that rapidly extracts a wide range of compounds, including the majority of organic acids and bitter compounds. Cold water, by contrast, is a much less efficient solvent for many of these components. This slower, gentler extraction process results in a coffee concentrate with a lower overall concentration of dissolved solids.
Crucially, cold water extracts fewer of the specific compounds linked to gastric irritation, such as N-alkanoyl-5-hydroxytryptamides. While the concentration of total chlorogenic acids in cold brew may not be dramatically lower than in a comparable hot brew, the cold method yields a lower concentration of total titratable acidity. This reduction in the total amount of acid and irritants explains why cold brew is often perceived as smoother and easier on the stomach.
Cold Brew Versus Conventional Coffee
The distinction between cold brew and hot brew often centers on acidity, but this term requires careful definition. When measuring the concentration of hydrogen ions using the pH scale, most studies find that the difference between cold and hot brew coffee is minimal, with both typically falling into a slightly acidic range around pH 4.8 to 5.2. Therefore, cold brew is not significantly “less acidic” in terms of pH.
However, the key difference lies in titratable acidity, which measures the total quantity of acidic compounds present in the solution. Cold brewing consistently produces a beverage with lower titratable acidity, meaning the total amount of acid available to interact with the digestive system is reduced. This lower concentration of total acids, combined with the decreased extraction of stomach-irritating compounds like N-alkanoyl-5-hydroxytryptamides, is what makes cold brew a gentler option.
For sensitive individuals, this chemical profile translates to a reduced likelihood of triggering reflux symptoms. Cold brew is not a universal cure for GERD, and it still contains caffeine, which can relax the LES and cause issues. However, by minimizing the total acid load and the presence of direct gastric irritants, cold brew offers a scientifically plausible and effective alternative for many coffee lovers with mild to moderate acid sensitivity.
Adjusting Coffee Habits for Sensitive Drinkers
Adjusting other coffee habits can be effective in managing symptoms.
Roast Level
Darker roasts are generally easier on the stomach than lighter roasts. Darker roasting breaks down more chlorogenic acids and creates N-methylpyridinium (NMP). NMP has been shown to reduce the stomach’s production of hydrochloric acid.
Timing and Consumption
The timing of consumption plays a considerable role in symptom management. Drinking coffee on an empty stomach intensifies irritation, as food is not present to buffer the stimulating effect on acid production. Consuming coffee with or immediately after a meal helps to dilute and neutralize the acids. Avoiding coffee and other trigger foods within two to three hours of bedtime prevents acid from easily flowing back when lying flat.
Water Quality and Additives
The quality of the water used for brewing can influence the final acidity; soft water tends to extract acidic compounds more efficiently. Be mindful of additives, as high-fat creamers and whole milk can sometimes trigger reflux by causing the lower esophageal sphincter to relax. Switching to low-fat or plant-based milks may help mitigate this effect.